after a few issues regarding re-soldering of the prototype board I thought it best to actually design the thing rather that just rely on the thoughts bouncing round my mind … I think I’ve remembered everything.
nano #1 reads the voltages of the battery and the charger and measures the current, it uses these to control the charging relay which disable the link between the battery and the charging spikes (after all we don’t want to create a weaponised lawnmower that can electrocute small children who get too close). It also controls the cutting blade motors.
nano #2 reads the edge sensors and the front and rear bumper resistor ladders.
nano #3 primarily controls the drive motors, in addition it reads the data from the 9DOF sensor on it’s own I2C bus.
The pi zero w communicates with nano’s #1&2 via I2C (with the pi being the master which allows it to run the bus at 3.3v), however as nano #3 is using I2C to communicate (as the master) with the 9DOF device it will communicate with the pi via I2C